// RxJS v6+
import { interval, of } from 'rxjs';
import { scan, delay, repeat, mergeMap } from 'rxjs/operators';

const fakeRequest = of('response').pipe(delay(2000));

// output:
// ['response'],
// ['response','response'],
// ['response','response','response'],
// etc...

interval(1000)
  .pipe(
    mergeMap(_ => fakeRequest),
    scan < string > ((all, current) => [...all, current], [])
  )
  .subscribe(console.log);

    public canActivate(
        context: ExecutionContext,
    ): boolean | Promise<boolean> | Observable<boolean> {
        const req: RequestGeneric<PostbackQueryInterface> | RequestGeneric<PostbackInterface> = context.switchToHttp().getRequest();
        if (this.isValid(req) === false) {
            throw new BadRequestException();
        }
        req.query = this.transform(req as RequestGeneric<PostbackQueryInterface>);
        return true;
    }